PT  - JOURNAL ARTICLE
AU  - Groer, C. E.
AU  - Tidgewell, K.
AU  - Moyer, R. A.
AU  - Harding, W. W.
AU  - Rothman, R. B.
AU  - Prisinzano, T. E.
AU  - Bohn, L. M.
TI  - An Opioid Agonist that Does Not Induce μ-Opioid Receptor—Arrestin Interactions or Receptor Internalization
AID  - 10.1124/mol.106.028258
DP  - 2007 Feb 01
TA  - Molecular Pharmacology
PG  - 549--557
VI  - 71
IP  - 2
4099  - http://molpharm.aspetjournals.org/content/71/2/549.short
4100  - http://molpharm.aspetjournals.org/content/71/2/549.full
SO  - Mol Pharmacol2007 Feb 01; 71
AB  - G protein-coupled receptor desensitization and trafficking are important regulators of opioid receptor signaling that can dictate overall drug responsiveness in vivo. Furthermore, different μ-opioid receptor (μOR) ligands can lead to varying degrees of receptor regulation, presumably because of distinct structural conformations conferred by agonist binding. For example, morphine binding produces a μOR with low affinity for β-arrestin proteins and limited receptor internalization, whereas enkephalin analogs promote robust trafficking of both β-arrestins and the receptors. Here, we evaluate μOR trafficking in response to activation by a novel μ-selective agonist derived from the naturally occurring plant product, salvinorin A. It is interesting that this compound, termed herkinorin, does not promote the recruitment of β-arrestin-2 to the μOR and does not lead to receptor internalization. Moreover, whereas G protein-coupled receptor kinase overexpression can promote morphine-induced β-arrestin interactions and μOR internalization, such manipulations do not promote herkinorin-induced trafficking. Studies in mice have shown that β-arrestin-2 plays an important role in the development of morphine-induced tolerance, constipation, and respiratory depression. Therefore, drugs that can activate the receptor without recruiting the arrestins may be a promising step in the development of opiate analgesics that distinguish between agonist activity and receptor regulation and may ultimately lead to therapeutics designed to provide pain relief without the adverse side effects normally associated with the opiate narcotics. The American Society for Pharmacology and Experimental Therapeutics